Earlier we have shown that many important properties of ionic aqueous channels in biological membranes can be imitated using simple biomimetic membranes. These membranes are composed of mixed cellulose ester-based filters, impregnated with isopropyl myristate or other esters of fatty acids, and can be used for high-throughput drug screening. If the membrane separates two aqueous solutions, combination of relatively hydrophilic polymer support with immobilized carboxylic groups results in the formation of thin aqueous layers covering inner surface of the pores, while the pore volume is filled by lipid-like substances. Because of these aqueous layers biomimetic membranes even without proteins have a cation/anion ion selectivity and specific (per unit of thickness) electrical properties, which are similar to typical properties of biological membranes. Here we describe frequency-dependent impedance of the isopropyl myristate-impregnated biomimetic membranes in the 4-electrode arrangement and present the results as Bode and Nyquist diagrams. When the membranes are placed in deionized water, it is possible to observe three different dispersion processes in the frequency range 0.1 Hz to 30 kHz. Only one dispersion is observed in 5 mM KH(2)PO(4) solution. It is suggested that these three dispersion features are determined by (a) conductivity in aqueous structures/channels, formed near the internal walls of the filter pores at high frequencies, (b) dielectric properties of the whole membrane at medium frequencies, determined by polymer support, aqueous layers and impregnating oil, and, finally, (c) by the processes in hydrated liquid crystal structures formed in pores by impregnating oil in contact with water at low frequencies.
[Show abstract][Hide abstract] ABSTRACT: Biomimetic membranes (BMM) based on polymer filters impregnated with lipids or their analogues are widely applied in numerous areas of physics, biology, and medicine. In this paper we report the design and testing of an electrochemical system, which allows the investigation of CO2 transport through natural membranes such as alveoli barrier membrane system and also can be applied for solid-state measurements. The experimental setup comprises a specially designed two-compartment cell with BMM connected with an electrochemical workstation placed in a Faraday cage, two PH meters, and a nondispersive infrared gas analyzer. We prove, experimentally, that the CO2 transport through the natural membranes under different conditions depends on pH and displays a similar behavior as natural membranes. The influence of different drugs on the CO2 transport process through such membranes is discussed.
Advances in Physical Chemistry 01/2011; 2011(5). DOI:10.1155/2011/210802
[Show abstract][Hide abstract] ABSTRACT: The conductivity of highly charged membranes is nearly constant, due to
counter-ions screening pore surfaces. Weakly charged porous media, or "leaky
membranes", also contain a significant concentration of co-ions, whose
depletion at high current leads to ion concentration polarization and
conductivity shock waves. To describe these nonlinear phenomena the absence of
electro-osmotic flow, a simple Leaky Membrane Model is formulated, based on
macroscopic electroneutrality and Nernst-Planck ionic fluxes. The model is
solved in cases of unsupported binary electrolytes: steady conduction from a
reservoir to a cation-selective surface, transient response to a current step,
steady conduction to a flow-through porous electrode, and steady conduction
between cation-selective surfaces in cross flow. The last problem is motivated
by separations in leaky membranes, such as shock electrodialysis. The article
begins with a tribute to Neal Amundson, whose pioneering work on shock waves in
chromatography involved similar mathematics.
[Show abstract][Hide abstract] ABSTRACT: Aquaporin attracted attention not only of physiologists and biophysicists, but also of chemical engineers. Here we critically analyze a paper describing aquaporin-based artificial membranes, suggested for forward osmosis-based water purification (Wang et al. 2012, Small 8, pp. 1185-1190). Related papers published later by the same group are also discussed. We indicate recently developed general approach to describe membrane transport, membrane permeability and selectivity, which is applicable for forward osmosis. In addition, we also mention our papers describing simple nitrocellulose-based membranes, which have selective aqueous channels without proteins, but successfully imitate many properties of biomembranes.
General Physiology and Biophysics 12/2013; 32(4):589-94. DOI:10.4149/gpb_2013058 · 1.17 Impact Factor
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